Semiconductor device having electrode made of high work function material, method and apparatus for manufacturing the same

ABSTRACT

Provided is a semiconductor device including a metal film which can be formed with lower costs but still mange to have a necessary work function and oxidation resistance. The semiconductor device includes an insulating film disposed on a substrate; and a metal film disposed on the insulating film. The metal film includes a stacked structure of: a first metal film disposed on the insulating film to directly contact the insulating film; a second metal film disposed on the first metal film to directly contact the first metal film; and the first metal film disposed on the second metal film to directly contact the second metal film, the second metal film having a work function greater than 4.8 eV and being different from the first metal film in material, wherein an oxidation resistance of the first metal film is greater than that of the second metal film.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 of Japanese Patent Application No. 2010-002256, filed onJan. 7, 2010, in the Japanese Patent Office, and is a continuationapplication of U.S. patent application Ser. No. 12/984,018, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device, a method ofmanufacturing a semiconductor device, and a substrate processingapparatus.

2. Description of the Related Art

To highly integrate metal-oxide-semiconductor field effect transistors(MOSFETs) and increase the performance of the MOSFETs, the use of ahigh-k/metal gate structure is considered, which is constituted by agate insulating film made of a high permittivity insulating material(high-k material) and a gate electrode made of a metal. In the case of ap-channel metal-oxide semiconductor (PMOS) transistor, it is preferablethat a gate electrode is made of a metal having a high work function ofabout 4.8 eV to 5.1 eV, and for example, it is considered that a gateelectrode is made of a noble metal such as platinum (Pt).

Furthermore, in the case of a dynamic random access memory (DRAM), it isconsidered that a capacitor insulating film is in de of a highpermittivity insulating material such as a hafnium dioxide (HfO₂), azirconium dioxide (ZrO₂), a titanium dioxide (TiO₂), a tantalumpentoxide (Ta₂O₅), and a niobium pentoxide (Nb₂O₅). In addition, a leakcurrent of a capacitor part can be effectively reduced by forming acapacitor electrode using a metal having a high work function. Thus,when a capacitor insulating film is made of HfO₂ or ZrO₂ having a wideband gap, a capacitor electrode is made of a material such as a titaniumnitride (TiN) having a work function of about 4.6 eV. In addition, whena capacitor insulating film is made of TiO₂ or Nb₂O₅ having a narrowband gap, a capacitor electrode is made of a noble metal such as Pthaving a high work function of about 5.1 eV.

However, if a metal film (for example, a gate electrode, a capacitorelectrode, etc.) made of an expensive noble metal such as Pt, themanufacturing costs of a semiconductor device may be increased. Inaddition, it is difficult to form a thin film by using a noble metalsuch as Pt. It can be considered that another metal having a high workfunction such as nickel (Ni) or cobalt (Co) is used instead of a noblemetal such as Pt. However, such a metal is easily oxidized, and if ametal film (a gate electrode or a capacitor electrode) is oxidized, theequivalent oxide thickness (EOT) of the metal film may be increased.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor deviceincluding a metal film which can be formed with lower costs but have anecessary work function and oxidation resistance. Another object of thepresent invention is to provide a method of manufacturing asemiconductor device and a substrate processing apparatus, which aredesigned to form a metal film having a necessary work function andoxidation resistance with lower costs.

According to an aspect of the present invention, there is provided asemiconductor device including: an insulating film disposed on asubstrate; and a metal film disposed on the insulating film, the metalfilm including a stacked structure of: a first metal film disposed onthe insulating film to directly contact the insulating film; a secondmetal film disposed on the first metal film to directly contact thefirst metal film; and the first metal film disposed on the second metalfilm to directly contact the second metal film, the second metal filmhaving a work function greater than 4.8 eV and being different from thefirst metal film in material, wherein an oxidation resistance of thefirst metal film is greater than that of the second metal film.

According to another aspect of the present invention, there is provideda method of manufacturing a semiconductor device, the method including:forming an insulating film on a substrate; and forming a metal filmincluding a stacked structure of: a first metal film disposed on theinsulating film to directly contact the insulating film; and a secondmetal film disposed on the first metal film to directly contact thefirst metal film, the second metal film having a work function greaterthan 4.8 eV and being different from the first metal film in material,wherein an oxidation resistance of the first metal film is greater thanthat of the second metal film.

According to another aspect of the present invention, there is provideda substrate processing apparatus including: a process chamber configuredto process a substrate; a first process gas supply system configured tosupply a first process gas into the process chamber to form a firstmetal film; a second process gas supply system configured to supply asecond process gas into the process chamber to form a second metal film;and a controller configured to control the first process gas supplysystem and the second process gas supply system, wherein an oxidationresistance of the first metal film is greater than that of the secondmetal film, the second metal film has a work function greater than 4.8eV and is different from the first metal film in material, and thecontroller controls the first process gas supply system and the secondprocess gas supply system to form a metal film having a stackedstructure of the first metal film and the second metal film adjacent toan insulating film disposed on the substrate by supplying the firstprocess gas and the second process gas into the process chamber wherethe substrate is accommodated such that the first metal film is formedbetween the second metal film and the insulating film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart for explaining substrate processing processesaccording to an embodiment of the present invention.

FIG. 2 is a view illustrating a gas supply system of a substrateprocessing apparatus relevant to the embodiment of the presentinvention.

FIG. 3 is a sectional view illustrating the substrate processingapparatus when a wafer is processed according to the embodiment of thepresent invention.

FIG. 4 is a sectional view illustrating the substrate processingapparatus when a wafer is carried according to the embodiment of thepresent invention.

FIG. 5A is a sectional view illustrating a gate electrode formed byperforming a TiN film-forming process and a Ni film-forming processonce, and FIG. 5B is sectional view illustrating a gate electrode formedby performing the TiN film-forming process and the Ni film-formingprocess a plurality of times.

FIG. 6A is a sectional view illustrating a capacitor electrode formed byperforming a TiN film-forming process and a Ni film-forming processonce, and FIG. 6B is sectional view illustrating a capacitor electrodeformed by performing the TiN film-forming process and the Nifilm-forming process a plurality of times.

FIG. 7 is a schematic view illustrating the energy level of aconventional capacitor electrode constituted by a single layer of TiNfilm.

FIG. 8 is a schematic view illustrating the energy levels of a metalfilm formed by performing a TiN film-forming process and a Nifilm-forming process once.

FIG. 9 is a schematic view illustrating the energy levels of a metalfilm formed by setting a TiN film-forming process and a Ni film-formingprocess as one cycle and performing the cycle a plurality of times.

FIG. 10 is a table illustrating a group of metals having work functionshigher than 4.8 eV which can be used for forming a second metal film.

FIG. 11 is a flowchart for explaining processes of forming an example 1(sample B) and a comparative example (sample C) illustrated in FIG. 12.

FIG. 12 is a schematic view for explaining the stacked structure of theexample 1 (sample B) of the present invention together with the stackedstructure of a conventional example (sample A) and the stacked structureof the comparative example (sample C).

FIG. 13 is a graph illustrating the equivalent oxide thicknesses (EOTs)of the samples A, B, and C illustrated in FIG. 12.

FIG. 14 is a graph illustrating relationships between leak currentdensities and EOTs of the respective samples A, B, and C illustrated inFIG. 12.

FIG. 15 is a graph illustrating relationships between leak currentdensities and applied voltages of the respective samples A, B, and Cillustrated in FIG. 12.

FIG. 16A is a schematic view illustrating the stacked structure of anexample 2 (sample D) of the present invention, and FIG. 16B is a graphillustrating a relationship between work function and TiN film thicknessof the sample D together with those of the sample B and sample C.

FIG. 17A and FIG. 17B are schematic views illustrating a verticalprocess furnace of a vertical apparatus according to another embodimentof the present invention, in which FIG. 17A is a vertical sectional viewillustrating the vertical process furnace and FIG. 17B is a sectionalview of the vertical process furnace taken along line A-A of FIG. 17A.

FIG. 18 is a schematic view illustrating a cluster apparatus accordingto another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

<Embodiment of Invention>

(1) Structure of Substrate Processing Apparatus

First, the structure of a substrate processing apparatus relevant to thecurrent embodiment will be described with reference to FIG. 3 and FIG.4. FIG. 3 is a sectional view illustrating the substrate processingapparatus when a wafer is processed according to an embodiment of thepresent invention, and FIG. 4 is a sectional view illustrating thesubstrate processing apparatus when the wafer is carried according tothe embodiment of the present invention.

(Process Chamber)

As shown in FIG. 3 and FIG. 4, the substrate processing apparatusrelevant to the current embodiments includes a process vessel 202. Forexample, the process vessel 202 is a flat airtight vessel having acircular cross sectional shape. In addition, the process vessel 202 ismade of a metal material such as aluminum or stainless steel (e.g., SUSdescribed in the Japanese industrial standard). In the process vessel202, a process chamber 201 is formed to process a substrate such as awafer 200 (e.g., a silicon wafer).

(Support Stage)

In the process chamber 201, a support stage 203 is installed to supporta wafer 200. On the top surface of the support stage 203 that makesdirect contact with the wafer 200, a susceptor 217 made of a materialsuch as quartz (SiO₂), carbon, a ceramic material, silicon carbide(SiC), aluminum oxide (Al₂O₃), or aluminum nitride (AlN) is installed asa support plate.

In the support stage 203, a heater 206 is built as a heating unit(heating source) configured to heat the wafer 200. The lower end part ofthe support stage 203 penetrates the bottom side of the process vessel202.

(Elevating Mechanism)

At the outside of the process chamber 201, an elevating mechanism 207 bis installed to raise and lower the support stage 203. By operating theelevating mechanism 207 b to raise and lower the support stage 203, thewafer 200 supported on the susceptor 217 can be raised and lowered. Whenthe wafer 200 is carried, the support stage 203 is lowered to a position(wafer carrying position) shown in FIG. 4, and when the wafer 200 isprocessed, the support stage 203 is raised to a position (waferprocessing position) shown in FIG. 3. The lower end part of the supportstage 203 is surrounded by a bellows 203 a so that the inside of theprocess chamber 201 can be hermetically maintained.

(Lift Pins)

In addition, on the bottom surface (floor surface) of the processchamber 201, for example, three lift pins 208 b are installed in amanner such that the lift pins 208 b are vertically erected.Furthermore, in the support stage 203 (including the susceptor 217),penetration holes 208 a are respectively formed at positionscorresponding to the lift pins 208 b so that the lift pins 208 b can beinserted through the penetration holes 208 a. Therefore, when thesupport stage 203 is lowered to the wafer carrying position, as shown inFIG. 4, upper parts of the lift pins 208 b protrude from the top surfaceof the susceptor 217 so that the lift pins 208 b can support the wafer200 from the bottom side of the wafer 200.

In addition, when the support stage 203 is raised to the waferprocessing position, as shown in FIG. 3, the lift pins 208 b areretracted from the top surface of the susceptor 217 so that thesusceptor 217 can support the wafer 200 from the bottom side of thewafer 2. Since the lift pins 208 b make direct contact with the wafer200, it is preferable that the lift pins 208 b are made of a materialsuch as quartz or alumina.

(Wafer Carrying Entrance)

At a side of the inner wall of the process chamber 201 (process vessel202), a wafer carrying entrance 250 is installed so that a wafer 200 canbe carried into and out of the process chamber 201 through wafercarrying entrance 250. At the wafer carrying entrance 250, a gate valve251 is installed so that the inside of the process chamber 201 cancommunicate with the inside of a carrying chamber (preliminary chamber)271 by opening the gate valve 251. The carrying chamber 271 is formed ina carrying vessel (airtight vessel) 272. In the carrying chamber 271, acarrying robot 273 is installed to carry a wafer 200. The carrying robot273 includes a carrying arm 273 a to support a wafer 200 when the wafer200 is carried. In a state where the support stage 203 is lowered to thewafer carrying position, if the gate valve 251 is opened, a wafer 200can be carried between the inside of the process chamber 201 and theinside of the carrying chamber 271 by using the carrying robot 273. Awafer 200 carried into the process chamber 201 is temporarily placed onthe lift pins 208 b as described above. In addition, at a side of thecarrying chamber 271 opposite to the wafer carrying entrance 250, aloadlock chamber (not shown) is installed, and a wafer 200 can becarried between the inside of the loadlock chamber and the inside of thecarrying chamber 271 by using the carrying robot 273. The loadlockchamber is used as a preliminary chamber to temporarily accommodate anon-processed or processed wafer 200.

(Exhaust System)

At a side of the inner wall of the process chamber 201 (process vessel202) opposite to the wafer carrying entrance 250, an exhaust outlet 260is installed for exhausting the inside atmosphere of the process chamber201. An exhaust pipe 261 is connected to the exhaust outlet 260 throughan exhaust chamber 260 a, and at the exhaust pipe 261, a pressureregulator 262 such as an auto pressure controller (APC) configured tocontrol the inside pressure of the process chamber 201, a sourcecollection trap 263, and a vacuum pump 264 are sequentially connected inseries. An exhaust system (exhaust line) is constituted mainly by theexhaust outlet 260, the exhaust chamber 260 a, the exhaust pipe 261, thepressure regulator 262, the source collection trap 263, and the vacuumpump 264.

(Gas Inlet)

At the top surface (the ceiling wall) of a shower head 240 (describedlater) installed at an upper part of the process chamber 201, a gasinlet 210 is installed to introduce various gases into the processchamber 201. A gas supply system connected to the gas inlet 210 will bedescribed later.

(Shower Head)

Between the gas inlet 210 and the process chamber 201, the shower head240 is installed as a gas distributing mechanism. The shower head 240includes a distributing plate 240 a configured to distribute a gasintroduced through the gas inlet 210, and a shower plate 240 bconfigured to distribute the gas passing through the distributing plate240 a more uniformly and supply the gas to the surface of the wafer 200placed on the support stage 203. A plurality of ventilation holes areformed in the distributing plate 240 a and the shower plate 240 b. Thedistributing plate 240 a is disposed to face the top surface of theshower head 240 and the shower plate 240 b, and the shower plate 240 bis disposed to face the wafer 200 placed on the support stage 203.Between the top surface of the shower head 240 and the distributingplate 240 a and between the distributing plate 240 a and the showerplate 240 b, spaces are provided which function as a first buffer space(distributing chamber) 240 c through which gas supplied through the gasinlet 210 is distributed a id a second buffer space 240 d through whichgas passing through the distributing plate 240 a is diffused.

(Exhaust Duct)

In the side surface of the inner wall of the process chamber 201(process vessel 202), a stopper 201 a is installed. The stopper 201 a isconfigured to hold a conductance plate 204 at a position adjacent to thewafer processing position. The conductance plate 204 is configured as adoughnut-shaped (ring-shaped) circular disk having an opening toaccommodate the wafer 200 in its inner circumferential part. A pluralityof discharge outlets 204 a are formed in the outer circumferential partof the conductance plate 204 in a manner such that the discharge outlets204 a are arranged at predetermined intervals in the circumferentialdirection of the conductance plate 204. The discharge outlets 204 a arediscontinuously formed so that the outer circumferential part of theconductance plate 204 can support the inner circumferential part of theconductance plate 204.

A lower plate 205 latches onto the outer circumferential part of thesupport stage 203. The lower plate 205 includes a ring-shaped concavepart 205 b and a flange part 205 a formed in one piece with the innerupper side of the concave part 205 b. The concave part 205 b isinstalled to close a gap between the outer circumferential part of thesupport stage 203 and the side surface of the inner wall of the processchamber 201. At a part of the lower side of the concave part 205 badjacent to the exhaust outlet 260, a plate exhaust outlet 205 c isformed to discharge (distribute) gas from the inside of the concave part205 b toward the exhaust outlet 260. The flange part 205 a functions asa latching part that latches onto the upper outer circumferential partof the support stage 203. Since the flange part 205 a latches onto theupper outer circumferential part of the support stage 203, the lowerplate 205 can be lifted together with the support stage 203 when thesupport stage 203 is lifted.

When the support stage 203 is raised to the wafer processing position,the lower plate 205 is also raised to the wafer processing position. Asa result, the top surface of the concave part 205 b of the lower plate205 is blocked by the conductance plate 204 held at a position adjacentto the wafer processing position, and thus a gas flow passage region isformed in the concave part 205 b as an exhaust duct 259. At this time,by the exhaust duct 259 (the conductance plate 204 and the lower plate205) and the support stage 203, the inside of the process chamber 201 isdivided into an upper process chamber higher than the exhaust duct 259and a lower process chamber lower than the exhaust duct 259. Preferably,the conductance plate 204 and the lower plate 205 may be formed of amaterial that is durable at a high temperature, for example, hightemperature resistant and high load resistant quartz, for the case wherereaction products deposited on the inner wall of the exhaust duct 259are etched away (for the case of self cleaning).

An explanation will now be given on a gas flow in the process chamber201 during a wafer processing process. First, gas supplied from the gasinlet 210 to the upper side of the shower head 240 flows from the firstbuffer space (distributing chamber) 240 c to the second buffer space 240d through the plurality of holes of the distributing plate 240 a, and isthen supplied to the inside of the process chamber 201 through theplurality of holes of the shower plate 240 b, so that the gas can beuniformly supplied to the wafer 200. Then, the gas supplied to the wafer200 flows outward in the radial directions of the wafer 200. After thegas makes contact with the wafer 200, remaining gas is discharged to theexhaust duct 259 disposed at the outer circumference of the wafer 200:that is, the remaining gas flows outward on the conductance plate 204 inthe radial directions of the wafer 200 and is discharged to the gas flowpassage region (the inside of the concave part 205 b) of the exhaustduct 259 through the discharge outlets 204 a formed in the conductanceplate 204. Thereafter, the gas flows in the exhaust duct 259 and isexhaust through the plate exhaust outlet 205 c and the exhaust outlet260. Since gas is guided to flow in this manner, the gas may beprevented from flowing to the lower part of the process chamber 201.That is, the gas may be prevented from flowing to the rear side of thesupport stage 203 or the bottom side of the process chamber 201.

<Gas Supply System>

Next, the configuration of the gas supply system connected to the gasinlet 210 will be described with reference to FIG. 2. FIG. 2 illustratesthe configuration of the gas supply system (gas supply lines) of thesubstrate processing apparatus relevant to the embodiment of the presentinvention.

The gas supply system of the substrate processing apparatus of thecurrent embodiment includes: a bubbler as a vaporizing unit configuredto vaporize a liquid source which is liquid at room temperature; asource gas supply system configured to supply a source gas, which isobtained by vaporizing the liquid source using the bubbler, into theprocess chamber 201; and a reaction gas supply system configured tosupply a reaction gas different from the source gas into the processchamber 201. In addition, the substrate processing apparatus of thecurrent embodiment includes a purge gas supply system configured tosupply a purge gas into the process chamber 201, and a vent (bypass)system so as not to supply a source gas generated from the bubbler intothe process chamber 201 but to exhaust the source gas through a passagebypassing the process chamber 201. Next, the structure of each part willbe described.

<Bubbler>

At the outside of the process chamber 201, a first source container(first bubbler) 220 a is installed which contains a first source (sourceA) which is a liquid source, and a second source container (secondbubbler) 220 b is installed which contains a second source (source B)which is a liquid source. Each of the first and second bubblers 220 aand 220 b is configured as a tank (airtight container) in which a liquidsource can be stored (filled). In addition, the first and second thebubblers 220 a and 220 b are configured as vaporizing units capable ofgenerating a first source gas and a second source gas by vaporizing afirst source and a second source through bubbling. In addition,sub-heaters 206 a are installed around the first bubbler 220 a and thesecond bubbler 220 b to heat the first and second bubblers 220 a and 220b and liquid sources filled in the first and second bubblers 220 a and220 b. For example, a metal liquid source containing titanium (Ti) suchas titanium tetrachloride (TiCl₄) may be used as the first source, and ametal liquid source containing nickel (Ni) such astetrakis(trifluorophosphine)nickel (Ni(PF₃)₄) may be used as the secondsource.

A first carrier gas supply pipe 237 a and a second carrier gas supplypipe 237 b are connected to the first bubbler 220 a and the secondbubbler 220 b, respectively. Carrier gas supply sources (not shown) areconnected to the upstream end parts of the first carrier gas supply pipe237 a and the second carrier gas supply pipe 237 b. In addition, thedownstream end parts of the first carrier gas supply pipe 237 a and thesecond carrier gas supply pipe 237 b are placed in the liquid sourcesfilled in the first bubbler 220 a and the second bubbler 220 h,respectively. A mass flow controller (MFC) 222 a which is a flow ratecontroller configured to control the supply flow rate of a carrier gas,and valves va1 and va2 configured to control supply of the carrier gasare installed at the first carrier gas supply pipe 237 a. A mass flowcontroller (MFC) 222 b which is a flow rate controller configured tocontrol the supply flow rate of a carrier gas, and valves vb1 and vb2configured to control supply of the carrier gas are installed at thesecond carrier gas supply pipe 237 b. Preferably, a gas that does notreact with the liquid sources may be used as the carrier gas. Forexample, inert gas such as N₂ gas and Ar gas may be used as the carriergas. A first carrier gas supply system (first carrier gas supply line)is constituted mainly by the first carrier gas supply pipe 237 a, theMFC 222 a, and the valves va1 and va2, and a second carrier gas supplysystem (second carrier gas supply line) is constituted mainly by thesecond carrier gas supply pipe 237 h, the MFC 222 b, and the valves vb1and vb2.

In the above-described structure, the valves va1, va2, vb1, and vb2 areopened, and a carrier gas the flow rates of which are controlled by theMFC 222 a and the MFC 222 b is supplied from the first carrier gassupply pipe 237 a and the second carrier gas supply pipe 237 b into thefirst bubbler 220 a and the second bubbler 220 b. Then, the liquidsources filled in the first and second bubblers 220 a and 220 b arevaporized by bubbling, and thus source gases are generated.

The supply flow rates of the first source gas and the second source gasmay be calculated from the supply flow rates of the carrier gas. Thatis, the supply flow rates of the first source gas and the second sourcegas may be controlled by adjusting the supply flow rates of the carriergas.

<Source Gas Supply System>

A first source gas supply pipe 213 a and a second source gas supply pipe213 b are respectively connected to the first bubbler 220 a and thesecond bubbler 220 b to supply the first source gas and the secondsource gas generated in the first bubbler 220 a and the second bubbler220 b into the process chamber 201. The upstream end parts of the firstand second source gas supply pipes 213 a and 213 b communicate withinner upper spaces of the first and second bubblers 220 a and 220 b. Thedownstream end parts of the first and second source gas supply pipes 213a and 213 b are joined together and then connected to the gas inlet 210.

In addition, valves va5 and va3 are sequentially installed from theupstream side of the first source gas supply pipe 213 a. The valve va5is configured to control supply of the first source gas from the firstbubbler 220 a to the first source gas supply pipe 213 a, and the valueva5 is installed at a position adjacent to the first bubbler 220 a. Thevalve va3 is configured to control supply of the first source gas fromthe first source gas supply pipe 213 a to the process chamber 201, andthe valve va3 is installed at a position adjacent to the as inlet 210.In addition, valves vb5 and vb3 are sequentially installed from theupstream side of the second source gas supply pipe 213 b. The valve vb5is configured to control supply of the second source gas from the secondbubbler 220 b to the second source gas supply pipe 213 b, and the valvevb5 is installed at a position adjacent to the second bubbler 220 b. Thevalve vb3 is configured to control supply of the second source gas fromthe second source gas supply pipe 213 b to the process chamber 201, andthe valve vb3 is installed at a position adjacent to the gas inlet 210.The valves va3 and vb3, and a valve ve3 (described later) arehighly-durable, high-speed values. Highly-durable, high-speed valves areintegrated valves configured to rapidly switch supply of gas,interruption of gas supply, and exhaustion of gas. The valve ve3controls introduction of a purge gas so as to rapidly purge a space ofthe first source gas supply pipe 213 a between the valve va3 and the gasinlet 210 and a space of the second source gas supply pipe 213 b betweenthe valve vb3 and the gas inlet 210, and then to purge the inside of theprocess chamber 201.

In the above-described structure, the liquid sources are vaporized inthe first and second bubblers 220 a and 220 b to generate the first andsecond source gases, and along with this, the valves va5, va3, vb5, andvb3 are opened, so that the first and second source gases can besupplied into the process chamber 201 from the first and second sourcegas supply pipes 213 a and 213 b. A first source gas supply system(first source gas supply line) is constituted mainly by the first sourcegas supply pipe 213 a and the valve va5 and va3, and a second source gassupply system (second source gas supply line) is constituted mainly bythe second source gas supply pipe 213 b and the valves vb5 and vb3.

A first source supply system (first source supply line) is constitutedmainly by the first carrier gas supply system, the first bubbler 220 a,and the first source gas supply system; and a second source supplysystem (second source supply line) is constituted mainly by the secondcarrier gas supply system, the second bubbler 220 b, and the secondsource gas supply system. A first process gas supply system isconstituted by the first source supply system and a reaction gas supplysystem (described later), and a second process gas supply system isconstituted by the second source gas supply system.

<Reaction Gas Supply System>

In addition, at the outside of the process chamber 201, a reaction gassupply source 220 c is installed to supply a reaction gas. The upstreamend part of a reaction gas supply pipe 213 c is connected to thereaction gas supply source 220 c. The downstream end part of thereaction gas supply pipe 213 c is connected to the gas inlet 210 througha valve vc3. An MFC 222 c which is a flow rate controller configured tocontrol the supply flow rate of a reaction gas, and valves vc1 and vc2configured to control supply of the reaction gas are installed at thereaction gas supply pipe 213 c. For example, ammonia (NH₃) gas may beused as the reaction gas. A reaction gas supply system (reaction gassupply line) is constituted mainly by the reaction gas supply source 220c, the reaction gas supply pipe 213 c, the MFC 222 c, and the valvesvc1, vc2, and vc3.

<Purge Gas Supply System>

In addition, at the outside of the process chamber 201, purge gas supplysources 220 d and 220 e are installed to supply a purge gas. Theupstream end parts of purge gas supply pipes 213 d and 213 e areconnected to the purge gas supply sources 220 d and 220 e, respectively.The downstream end part of the purge gas supply pipe 213 d is joined tothe reaction gas supply pipe 213 c and is connected to the gas inlet 210through the valve vc3. The downstream end part of the purge gas supplypipe 213 e is joined to the first source gas supply pipe 213 a and thesecond source gas supply pipe 213 b and is connected to the gas inlet210 through the valve ve3. At the purge gas supply pipes 213 d and 213e, MFCs 222 d and 222 e are respectively installed as flow ratecontrollers configured to control the supply flow rates of purge gas,and valves vd1, vd2, ve1, and ve2, are respectively installed to controlsupplies of purge gas. For example, inert gas such as N₂ gas and Ar gasmay be used as a purge gas. A purge gas supply system (purge gas supplyIII s constituted mainly by the purge gas supply sources 220 d and 220e, the purge gas supply pipes 213 d and 213 e, the MFCs 222 d and 222 e,the valves vd1, vd2, vc3, ve1, ve2, and ve3.

<Vent (Bypass) System>

In addition, the upstream end parts of a first vent pipe 215 a and asecond vent pipe 215 b are respectively connected to the upstream sidesof the valves va3 and vb3 of the first and second source gas supplypipes 213 a and 213 b. In addition, the downstream end parts of thefirst and second vent pipes 215 a and 215 b are joined together andconnected between the downstream side of the pressure regulator 262 andthe upstream side of the source collection trap 263 of the exhaust pipe261. At the first and second vent pipes 215 a and 215 b, valves va4 andvb4 are respectively installed to control flows of gases.

In the above-described structure, by closing the valves va3 and vb3 andopening the valves va4 and vb4, gases flowing in the first and secondsource gas supply pipes 213 a and 213 b can be allowed to bypass theprocess chamber 201 through the first and second vent pipes 215 a and215 b without being supplied into the process chamber 201, and then thegases can be exhausted to the outside of the process chamber 201 throughthe exhaust pipe 261. A first vent system is constituted mainly by thefirst vent pipe 215 a, the valve va4, and a second vent system isconstituted mainly by the second vent pipe 215 b and the valve vb4.

The sub-heaters 206 a are also installed around the first and secondvent pipes 215 a and 215 b. In addition, the sub-heaters 206 a are alsoinstalled around other members such as the first carrier gas supply pipe237 a, the second carrier gas supply pipe 237 b, the first source gassupply pipe 213 a, the second source gas supply pipe 213 b, the exhaustpipe 261, the process vessel 202, and the shower head 240. Thesub-heater 206 a is configured to heat such members to, for example,100° C. or lower, so as to prevent the first and second source gasesfrom changing back to liquid in the members.

<Controller>

The substrate processing apparatus relevant to the current embodimentincludes a controller 280 configured to control each part of thesubstrate processing apparatus. The controller 280 controls operationsof parts such as the gate valve 251, the elevating mechanism 207 b, thecarrying robot 273, the heater 206, the sub-heater 206 a, the pressureregulator (APC) 262, the vacuum pump 264, the valves va1 to va5, vb1 tovb5, vet to vc3, vd1 and vd2, and ve1 to ve3, and the MFCs 222 a, 222 b,222 c, 222 d, and 222 e.

(2) Substrate Processing Processes

Next, with reference to FIG. 1, as one of semiconductor devicemanufacturing processes, a substrate processing process for forming athin film on a wafer by a chemical vapor deposition (CVD) method and anatomic layer deposition (ALD) method using the above-described substrateprocessing apparatus will be explained according to the embodiment ofthe present invention. FIG. 1 is a flowchart for explaining substrateprocessing processes according to the embodiment of the presentinvention. In the following description, operations of partsconstituting the substrate processing apparatus are controlled by thecontroller 280.

In the following description, an explanation will be given on anexemplary case where a metal film having a stacked structure constitutedby a TiN film being a first metal film and a Ni film being a secondmetal film is formed on a TiO₂ film which is previously formed on asubstrate such as a wafer 200 as an insulating film (gate insulatingfilm or capacitor insulating film).

The TiN film which is a first metal film is formed according to an ALDmethod by alternately supplying a first source gas (Ti source), which isgenerated by vaporizing a first source (TiCl₄), and a reaction gas (NH₃gas) into the process chamber 201 in which the wafer 200 isaccommodated. The Ni film which is a second metal film is formedaccording to a CVD method by supplying a second source gas (Ni source)generated by vaporizing a second source (Ni(PF₃)₄) into the processchamber 201 in which the wafer 200 is accommodated. The first source gasand the reaction gas constitute a first process gas, and the secondsource gas constitutes a second process gas.

In this specification, the term “metal film” is used to denote a filmformed of a conductive material containing metal atoms. Examples thereofinclude a conductive elemental metal film formed of an elemental metal,a conductive metal nitride film, a conductive metal oxide film, aconductive metal oxynitride film, a conductive metal composite film, aconductive metal alloy film, and a conductive metal suicide film. TheTiN film is a conductive metal nitride film, and the Ni film is aconductive elemental metal film. The exemplary case will now beexplained in detail.

<Substrate Carrying-In Process S1, Substrate Placing Process S2>

First, the elevating mechanism 207 b is operated to lower the supportstage 203 to the wafer carrying position as shown in FIG. 4. Next, thegate valve 251 is opened so that the process chamber 201 can communicatewith the carrying chamber 271. Next, a wafer 200 to be processed iscarried from the carrying chamber 271 to the process chamber 201 byusing the carrying robot 273 in a state where the wafer 200 is supportedon the carrying arm 273 a (S1). A TiO₂ film is previously formed as aninsulating film (gate insulating film or capacitor insulating film) onthe wafer 200 to be processed. The wafer 200 loaded in the processchamber 201 is temporarily placed on the lift pins 208 b which protrudeupward from the top surface of the support stage 203. Thereafter, thecarrying arm 273 a of the carrying robot 273 is moved from the inside ofthe process chamber 201 back to the carrying chamber 271, and the gatevalve 251 is closed.

Next, the elevating mechanism 207 b is operated to raise the supportstage 203 to the wafer processing position as shown in FIG. 3. As aresult, the lift pins 208 b are retracted from the top surface of thesupport stage 203, and the wafer 200 is placed on the susceptor 217disposed at the top surface of the support stage 203 (S2).

<Pressure Adjusting Process S3, Temperature Adjusting Process S4)

Subsequently, by using the pressure regulator (APC) 262, the insidepressure of the process chamber 201 is adjusted to a predeterminedprocess pressure (S3). In addition, power supplied to the heater 206 iscontrolled to increase the surface temperature of the wafer 200 to apredetermined process temperature (S4). The temperature adjustingprocess S4 may be performed in parallel with or prior to the pressureadjusting process S3. The predetermined process temperature and processpressure are set in a manner such that a TiN film can be formed in a TiNfilm-forming process S5 (described later) by an ALD method. That is, theprocess temperature and the process pressure are set in a manner suchthat a first source gas supplied in a Ti source supply process S5 a doesnot decompose by itself.

In the substrate carrying-in process S1, the substrate placing processS2, the pressure adjusting process S3, and the temperature adjustingprocess S4, the vacuum pump 264 is operated in a state where the valvesva3 and vb3 are closed and the valves vd1, vd2, vc3, ve1, ve2, and ve3are opened, so as to create a flow of N₂ gas in the process chamber 201.By this, adhesion of particles to the wafer 200 can be suppressed.

Along with the processes S1 to S4, a first source (TiCl₄) is vaporizedto generate a first source gas (Ti source). That is TiCl₄ gas isgenerated (preliminary vaporization). That is, the valves va1, va2, andva5 are opened, and a carrier gas the flow rate of which is controlledby the MFC 222 a is supplied from the first carrier gas supply pipe 237a into the first bubbler 220 a so as to vaporize a first source filledin the first bubbler 220 a by bubbling to generate a first source gas(preliminary vaporization process). In this preliminary vaporizationprocess, while operating the vacuum pump 264, the valve va4 is opened ina state where the valve va3 is closed, so that the first source gas isnot supplied into to the process chamber 201 but is exhausted through aroute bypassing the process chamber 201. A predetermined time isnecessary for the first bubbler 220 a to stably generate the firstsource gas. For this reason, in the current embodiment, the first sourcegas is preliminary generated, and the flow passage of the first sourcegas is changed by selectively opening and closing the valves va3 andva4. That is, by selectively opening and closing the valves va3 and va4,stable supply of the first source gas into the process chamber 201 canbe quickly started and stopped. This operation is preferable.

<TiN Film-Forming Process S5>

(Ti Source Supply Process S5 a)

Next, while operating the vacuum pump 264, the valve va4 is closed andthe valve va3 is opened to start supply of the first source gas (Tisource) into the process chamber 201.

The first source gas is distributed by the shower head 240 so that thefirst source gas can be uniformly supplied to the wafer 200 disposed inthe process chamber 201. Surplus first source gas flows in the exhaustduct 259 and is exhausted to the exhaust outlet 260 and the exhaust pipe261. At this time, the process temperature and process pressure are setin a manner such that the first source gas does not decompose by itself.Therefore, molecules of the first source gas are adsorbed on the TiO₂film which is previously formed on the wafer 200 as an insulating film(gate insulating film or capacitor insulating film).

When the first source gas is supplied into the process chamber 201, soas to prevent permeation of the first source gas into the reaction gassupply pipe 213 c and facilitate diffusion of the first source gas inthe process chamber 201, it is preferable that the valves vc1, vc2, andvc3 are kept in an opened state to continuously supply N₂ gas into theprocess chamber 201.

After a predetermined time from the start of supply of the first sourcegas by opening the valve va3, the valve va3 is closed, and the valvesva4 is opened to stop supply of the first source gas into the processchamber 201.

(Purge Process S5 b)

After stopping supply of the first source gas by closing the valve va3,the valves vd1, vd2, vc3, ve1, ve2, and ve3 are opened to supply N₂ gasinto the process chamber 201. The N₂ gas is dispersed by the shower head240 and uniformly supplied to the wafer 200 disposed in the processchamber 201, and then the N₂ gas flows in the exhaust duct 259 and isexhausted to the exhaust outlet 260 and the exhaust pipe 261. In thisway, the first source gas remaining in the process chamber 201 isremoved, and the inside of the process chamber 201 is purged with N₂gas.

(Reaction Gas Supply Process S5 c)

After the inside of the process chamber 201 is purged, the valves vc1,vc2, and vc3 are opened to start supply of a reaction gas (NH₃ gas) intothe process chamber 201. The reaction gas is dispersed by the showerhead 240 and uniformly supplied to the wafer 200 disposed in the processchamber 201 so that the reaction gas reacts with the molecules of thefirst source gas adsorbed on the TiO₂ film previously formed on thewafer 200. Thus, a TiN film constituted by about less than one atomiclayer less than 1 Å) is formed on the TiO₂ film. Surplus reaction gas orreaction byproducts are allowed to flow in the exhaust duct 259 and areexhausted to the exhaust outlet 260 and the exhaust pipe 261. After apredetermined time from the start of supply of the reaction gas byopening the valve vc1, vc2, and vc3, the supply of the reducing gas intothe process chamber 201 is interrupted by closing the valves vc1 andvc2.

When the reaction gas is supplied into the process chamber 201, so as toprevent permeation of the reaction gas into the first source gas supplypipe 213 a and the second source gas supply pipe 213 b and facilitatediffusion of the reaction gas in the process chamber 201, it ispreferable that the valves ve1, ve2, and ve3 are kept opened to continuesupply of N₂ gas into the process chamber 201.

(Purge Process S5 d)

After stopping supply of the reaction gas by closing the valve vc1 andvc2, the valves vd1, vd2, vc3, ve1, ve2, and ve3 are opened to supply N₂gas into the process chamber 201. The N₂ gas is dispersed by the showerhead 240 and uniformly supplied to the wafer 200 disposed in the processchamber 201, and then the N₂ gas flows in the exhaust duct 259 and isexhausted to the exhaust outlet 260 and the exhaust pipe 261.

In this way, reaction gas and reaction byproducts remaining in theprocess chamber 201 are removed, and the inside of the process chamber201 is purged with the N₂ gas.

(Predetermined-Time Executing Process S5 e)

The Ti source supply process S5 a, the purge process S5 b, the reactiongas supply process S5 c, and the purge process S5 d are set as onecycle, and the cycle (ALD cycle) is performed predetermined times (n1cycles) so that a titanium nitride (TiN) film having a predeterminedthickness can be formed as a first metal film on the TiO₂ filmpreviously formed on the wafer 200. The TiN film which is a first metalfilm has an oxidation resistance greater than that of a Ni film thatwill be formed as a second metal film (described later).

<Pressure Adjusting Process S6, Temperature Adjusting Process S7)

Subsequently, by using the pressure regulator (APC) 262, the insidepressure of the process chamber 201 is adjusted to a predeterminedprocess pressure (S6). In addition, power supplied to the heater 206 iscontrolled to increase the surface temperature of the wafer 200 to apredetermined process temperature (S7). The temperature adjustingprocess S7 may be performed in parallel with or prior to the pressureadjusting process S6. The predetermined process temperature and processpressure are set in a manner such that a Ni film can be formed in a Nifilm-forming process S8 (described later) by a CVD method. That is, theprocess temperature and the process pressure are set in a manner suchthat a second source gas supplied in a Ni source supply process S8 a candecompose by itself.

Along with the pressure adjusting process S6 and the temperatureadjusting process S7, a second source (Ni(PF₃)₄) is vaporized topreviously generate a second source gas (Ni source), that is, Ni(PF₃)₄gas for the next Ni film-forming process S8 (preliminary vaporization).That is, the valves vb1, vb2, and vb5 are opened, and a carrier gas, theflow rate of which is controlled by the MFC 222 b, is supplied from thesecond carrier gas supply pipe 237 b into the second bubbler 220 b so asto vaporize a second source filled in the second bubbler 220 b bybubbling to generate a second source gas (preliminary vaporizationprocess). In this preliminary vaporizing process, while operating thevacuum pump 264, the valve vb4 is opened in a state where the vb3 isclosed so as not to supply the second source gas into the processchamber 201 but exhaust the second source gas through a route bypassingthe process chamber 201. A predetermined time is necessary for thesecond bubbler 220 b to stably generate the second source gas. For thisreason, in the current embodiment, the second source gas is preliminarygenerated, and the flow passage of the second source gas is changed byselectively opening and closing the valves vb3 and vb4. That is, byselectively opening and closing the valves vb3 and vb4, stable supply ofthe second source gas into the process chamber 201 can be quicklystarted and stopped. This operation is preferable.

<Film-Forming Process S8>

(Ni Source Supply Process S8 a)

Next, while operating the vacuum pump 264, the valve va4 is closed andthe valve va3 is opened to supply the second source gas (Ni source) intothe process chamber 201. The second source gas is distributed by theshower head 240 so that the second source gas can be uniformly suppliedto the wafer 200 disposed in the process chamber 201. Surplus secondsource gas flows in the exhaust duct 259 and is exhausted to the exhaustoutlet 260 and the exhaust pipe 261. At this time, the processtemperature and process pressure are set in a manner such that thesecond source gas can decompose. Therefore, the second source gassupplied to the wafer 200 thermally decomposes and participates in a CVDreaction, and accordingly a Ni film is formed on the wafer 200.

When the second source gas is supplied into the process chamber 201, soas to prevent permeation of the second source gas into the reaction gassupply pipe 213 c and facilitate diffusion of the second source gas inthe process chamber 201, it is preferable that the valves vd1, vd2, andvd3 are kept in an opened state to continuously supply N₂ gas into theprocess chamber 201.

After a predetermined time from the start of supply of the second sourcegas by opening the valve vb3, the valve vb3 is closed and the valves vb4is opened to stop supply of the second source gas into the processchamber 201.

(Purge Process S8 b)

After stopping supply of the second source gas by closing the valve vb3,the valves vd1, vd2, vc3, ve1, ve2, and ve3 are opened to supply N₂ gasinto the process chamber 201. The N₂ gas is dispersed by the shower head240 and supplied into the process chamber 201, and then the N₂ gas flowsin the exhaust duct 259 and is exhausted to the exhaust outlet 260 andthe exhaust pipe 261. In this way, the second source gas remaining inthe process chamber 201 is removed, and the inside of the processchamber 201 is purged with N₂ gas.

(Predetermined-time executing process S8 c)

The Ni source supply process S8 a and the purge process S8 b are set asone cycle, and the cycle is performed predetermined times (n2 cycles) sothat a nickel film (Ni film) having a predetermined thickness can beformed as a second metal film on the TiN film which is formed as a firstmetal film over the wafer 200. The Ni film which is a second metal filmis made of a material having a work function greater than 4.8 eV anddifferent from a material used to form the first metal film.

<Predetermined-Time Executing Process S9>

The pressure adjusting process 53 to the TiN film-forming process S5 andthe pressure adjusting process S6 to the Ni film-forming process S8 areset as one cycle, and the cycle is performed predetermined times (n3cycles) so that a metal film having a stacked structure constituted bythe TiN film being the first metal film and the Ni film being the secondmetal film can be formed on the TiO₂ film previously formed on the wafer200. As described above, the TiN film which is the first metal film hasan oxidation resistance greater than the oxidation resistance of the Nifilm which is the second metal film. In addition, the Ni film which isthe second metal film is made of a material having a work functiongreater than 4.8 eV and being different from the first metal film. TheTiN film which is the first metal film is formed between the Ni film(second metal film) and the TiO₂ film.

<Pressure Adjusting Process S10, Temperature Adjusting Process S11)

Next, like in the pressure adjusting process S3 and the temperatureadjusting process S4, the inside pressure of the process chamber 201 isadjusted to a predetermined process pressure (S10), and the surfacetemperature of the wafer 200 is adjusted to a predetermined processtemperature (S11).

<TiN Cap Forming Process S12>

(Ti Source Supply Process S12 a)

Next, like in the Ti source supply process S5 a, the first source gas(Ti source) is supplied into the process chamber 201 for a predeterminedtime, and then the supply of the first source gas into the processchamber 201 is stopped.

(Purge Process S12 b)

After stopping the supply of first source gas, the inside of the processchamber 201 is purged with N₂ gas like in the purge process S5 b.

(Reaction Gas Supply Process S12 c)

After the inside of the process chamber 201 is purged, like in thereaction gas supply process S5 c, the reaction gas (NH₃ gas) is suppliedinto the process chamber 201 for a predetermined time, and then thesupply of the reaction gas into the process chamber 201 is stopped.

(Purge Process S12 d)

After stopping the supply of the reaction gas, the inside of the processchamber 201 is purged with N₂ gas like in the purge process S5 d.

(Predetermined-Time Executing Process S12 e)

The Ti source supply process S12 a, the purge process S12 b, thereaction gas supply process S12 c, and the purge process S12 d are setas one cycle, and the cycle is performed predetermined times (n4 cycles)so that a TiN film (TiN cap film) having a predetermined thickness canbe formed as a first metal film on the metal film (having a stackedstructure constituted by TiN film and Ni film) formed through thepredetermined-time executing process S9.

By performing the processes S3 to S12, the metal film can be formedadjacent to the TiO₂ film which is previously formed on the wafer 200 asan insulating film (gate insulating film or capacitor insulating film).The metal film has a stacked structure constituted by the TiN film whichis the first metal film and the Ni film which is the second metal film.The first metal film is made of a material (TiN) having an oxidationresistance greater than the oxidation resistance of the second metalfilm, and the second metal film is made of a material (Ni) having a workfraction greater than 4.8 eV and being different from the material usedto make the first metal film. In addition, the TiN film is formedbetween the Ni film and the TiO₂ film. Furthermore, the TiN film (TN capfilm) is formed on the outermost surface of the metal film. If theexecution number n3 cycles) of the predetermined-time executing processS9 is set to one (one cycle), a metal film can be formed as a gateelectrode as shown in FIG. 5A or a top capacitor electrode as shown inFIG. 6A. If the execution number (n3 cycles) of the predetermined-timeexecuting process S9 is set to two or more (two or more cycles), a metalfilm can be formed as a gate electrode as shown in FIG. 5B or a topcapacitor electrode as shown in FIG. 6B. A bottom capacitor electrode asshown in FIG. 6B may also be formed through a process similar to theprocess of forming the top capacitor electrode.

<Remaining Gas Removing Process S13>

After the TiN cap film having a predetermined thickness is formed on themetal film (having a stacked structure constituted by TN film and Nifilm) formed through the predetermined-time executing process S9, theinside of the process chamber 201 is vacuum-evacuated, and the valvesvd1, vd2, vc3, ve1, ve2, and ve3 are opened to supply N₂ gas into theprocess chamber 201. The N₂ gas is dispersed by the shower head 240 andsupplied into the process chamber 201, and then the N₂ is exhausted tothe exhaust pipe 261. In this way, gas and reaction byproducts remainingin the process chamber 201 are removed, and the inside of the processchamber 201 is purged with the N₂ gas.

<Substrate Carrying-Out Process S14>

Thereafter, in the reverse order to that of the substrate carrying-inprocess S1 and the substrate placing process S2, the wafer 200, overwhich the metal film (having a stacked structure constituted by TiN filmand Ni film) and the TiN cap film are formed to predeterminedthicknesses, is carried out from the process chamber 201 to the carryingchamber 271, thereby completing the substrate processing process of thecurrent embodiment.

Furthermore, in the current embodiment, the TiN film-forming process S5may be performed to a wafer 200 under the following exemplaryconditions.

Process temperature: 250° C. to 550° C., preferably, 350° C. to 550° C.,

Process pressure: 50 Pa to 5,000 Pa,

Supply flow rate of carrier gas (N₂) for bubbling: 10 sccm to 1,000sccm,

Supply flow rate of first source gas (TiCl₄): 0.1 sccm to 2 sccm,

Supply flow rate of reaction gas (NH₃): 10 sccm to 1,000 sccm,

Supply flow rate of purge gas (N₂): 100 sccm to 10,000 sccm, and

Film thickness (TiN film): 0.2 nm to 4 nm.

Furthermore, in the current embodiment, the Ni film-forming process S8may be performed to a wafer 200 under the following exemplaryconditions.

Process temperature: 150° C. to 250° C., preferably, 150° C. to 200° C.,

Process pressure: 50 Pa to 5,000 Pa,

Supply flow rate of carrier gas (N₂) for bubbling: 10 sccm to 1,000sccm,

Supply flow rate of second source gas (Ni(PF₃)₄): 0.1 sccm to 2 sccm,

Supply flow rate of purge gas (N₂): 100 sccm to 10,000 sccm, and

Film thickness film): 0.5 nm to 10 nm, preferably, 4 nm to 5 nm.

In addition, total film thickness in the predetermined-time executingprocess S9, that is, the thickness of a metal film having a stackedstructure constituted by TiN film being first metal film and Ni filmbeing second metal film may be, for example, 10 nm to 30 nm.

Furthermore, in the current embodiment, the TiN cap film-forming processS12 may be performed to a wafer 200 under the following exemplaryconditions.

Process temperature: 250° C. to 550° C., preferably, 350° C. to 550° C.,

Process pressure: 50 Pa to 5,000 Pa,

Supply flow rate of carrier gas (N₂) for bubbling: 10 sccm to 1,000sccm,

Supply flow rate of first source gas (TiCl₄): 0.1 sccm to 2 sccm,

Supply flow rate of reaction gas (NH₃): 10 sccm to 1,000 sccm,

Supply flow rate of purge gas (N₂): 100 sccm to 10,000 sccm, and

Film thickness (TiN film): 0.2 nm to 50 nm, preferably, 1 nm to 10 nm,

If a TiN film is formed to have a thickness of less than 0.2 nm in theTiN film-forming process S5, the TiN film may not be constituted by oneor more continuous layers between a Ni film and a TiO₂ film. That is,the TiN film may be constituted by a discontinuous layer, and thus theNi film and the TiO₂ may make contact with each other. Therefore, anoxygen component included in the TiO₂ film may permeate into the Ni filmthrough a contact part, and thus the Ni film may be oxidized. Inaddition, if a TiN film is formed to have a thickness greater than 4 nmin the TiN film-forming process S5, the effective work function of anentire metal film may not be the work function of a Ni film (about 5.15eV) but may be close to the work function of the TiN film (about 4.6eV). Thereafter, it is preferable that a TiN film is formed to have athickness of 0.2 nm to 4 nm in the TiN film-forming process S5.

In addition, if the process temperature of the Ni film-forming processS8 is lower than 150° C., in the Ni film-forming process S8 a, thesecond source (Ni(PF₃)₄) may not decompose by itself, and thus, a CVDfilm-forming reaction may not occur. In addition, if the processtemperature is higher than 250° C. in a state where the process pressureis kept in the above-mentioned range, the film-forming rate may increaseexcessively, and thus it may be difficult to control a film thickness.Therefore, in the Ni film-forming process S8, it is necessary to keepthe process temperature in the range from 150° C. to 250° C. forinducing a CVD film-forming reaction and controlling a film thickness.

In the current embodiment, it is preferable that the TiN film-formingprocess S5 and the Ni film-forming process S8 are performed at the sameprocess temperature and/or the same process pressure. That is, in thecurrent embodiment, it is preferable that the TiN film-forming processS5 and the Ni film-forming process S8 are performed at a constantprocess temperature and/or a constant process pressure. If the processtemperature and the process pressure are set to predetermined values inthe above-mentioned ranges, ALD film formation and CVD film formationcan be performed under the same conditions. In this case, when theprocedure goes from the TiN film-forming process S5 to the Nifilm-forming process S8 or from the Ni film-forming process S8 to theTiN film-forming process S5, a process of changing the processtemperature and a process of changing the process pressure may not benecessary, and thus the throughput may be improved.

(3) Effects of the Embodiment

According to the current embodiment, one or more of the followingeffects can be obtained.

(a) According to the current embodiment, the TiN film having anoxidation resistance greater than that of the Ni film is formed as thelowermost layer of the metal film, that is, the layer (interfacialsurface) between the Ni film and the TiO₂ film. Since the TiN film hasan oxidation resistance greater than that of the Ni film, for example,when the Ni film is formed by a CVD method or the wafer 200 on which themetal film is formed is heated to about 400° C. to perform an annealingtreatment, it can be prevented that the Ni film is oxidized by an oxygencomponent permeated from the TiO₂ film into the Ni film through aninterfacial surface therebetween. Particularly, in the currentembodiment, the TiN film is formed to have a thickness of 0.2 nm orgreater in the TiN film-forming process S5. Thus, the TiN film formedbetween the Ni film and the TiO₂ film can be surely constituted by oneor more continuous layers, and thus the Ni film and the TiO₂ film can beprevented from directly making contact with each other and oxidation ofthe Ni film can be effectively suppressed. Hence, oxidation of the metalfilm can be suppressed, and an increase of equivalent oxide thickness(EOT) can be prevented.

(b) In addition, according to the current embodiment, the TN film (TiNcap layer) having an oxidation resistance greater than that of the Nifilm is formed as the uppermost layer of the metal film, that is, theexposed surface layer of the metal film. Thus, permeation of oxygen fromthe atmosphere to the Ni film through the exposed surface of the metalfilm can be prevented, and thus oxidation of the Ni film can besuppressed. For example, when the wafer 200 on which the metal film isexposed is carried for the next process, it can be prevented that the Nifilm is oxidized at room temperature by oxygen permeated into the Nifilm from the atmosphere through the exposed surface of the metal film.Particularly, according to the current embodiment in the TiN cap formingprocess S12, the TiN film is formed to have a thickness of 0.2 nm to 50nm, preferably, 1 nm to 10 nm, and thus the TiN film covering thesurface of the Ni film can be surely constituted by one or morecontinuously layers. Therefore, the Ni film can be prevented from makingdirect contact with the atmosphere, and thus oxidation of the Ni filmcan be effectively suppressed. Hence, oxidation of the metal film can besuppressed, and an increase of EOT can be prevented.

(c) In addition, according to the current embodiment, the second metalfilm is formed of Ni (different from the first metal film in material)having a work function greater than 4.8 eV. Although the work functionof TiN used to form the first metal film is estimated to be 4.6 eV, thework function of Ni is 5.15 eV as shown in FIG. 10. Thus, the effectivework function of the entire metal film having a stacked structureconstituted by the TiN film and the Ni film can be close to the workfunction of the Ni film (about 5.15 eV). Particularly, according to thecurrent embodiment, the thickness of the Ni film formed in the Nifilm-forming process S8 is greater than the thickness of the TN filmformed in the TiN film-forming process S5. Thus, the effect of the workfunction of the thicker Ni film is increased, and thus the effectivework function of the entire work function of the metal film having astacked structure constituted by the TiN film and the Ni film can becloser to the work function of the Ni film (about 5.15 eV). Therefore,when the metal film is used as a capacitor electrode, a leak current ofa capacitor part can be reduced.

For example, if a metal film as shown in FIG. 5A or FIG. 6A is formed byperforming the TiN film-forming process S5 and the Ni film-formingprocess S8 once in a manner such that a TiN film is formed to have athickness ranging from 0.2 nm to 4 nm in the TiN film-forming process S5and a thicker Ni film is formed to have a thickness ranging from 0.5 nmto 10 nm, preferably, 4 nm to 5 nm in the Ni film-forming process S8,the effect of the work function of the thicker Ni film is high so thatthe effective work function of the entire metal film can approach about5.0 eV. For example, when a metal film as shown in FIG. 5B or FIG. 6B isformed by setting the TiN film-forming process S5 and the Nifilm-forming process S8 as one cycle and performing the cycle aplurality of times, the effective work function of the entire metal filmcan be adjusted to a desired value. That is, in this case, since thework functions of TiN films and Ni films are affected by each other, theeffective work function of the entire metal film can be adjusted to adesired value between 4.6 eV and 5.0 eV by adjusting a thickness ratioof the TiN films and the Ni films. In either case, if the thickness ofthe TiN film formed in the TiN film-forming process S5 is greater than 4nm, the effective work function of the entire metal film may bedecreased to be close to the work function (4.6 eV) of the TiN film.

FIG. 7 is a schematic view illustrating the energy level of aconventional capacitor electrode constituted by a single layer of TiNfilm. The leak current of a capacitor structure (metal-insulator-metal(MIM) structure), in which a capacitor insulating film (for example, aTiO₂ film) is disposed between TiN films, is determined mainly by thework function of capacitor electrodes and the band offset (conductionband offset) of the conduction band side of the capacitor insulatingfilm. Since a voltage of ±1 V is generally applied between capacitorelectrodes, it is preferable that a conduction band offset is greaterthan 1.0 eV. In addition, since the work function of TiN is about 4.6eV, if a TiO₂ film is used as a capacitor insulating film, a conductionband offset of only about 1.0 eV may be ensured, and thus leak currentmay be increased.

However, if the metal film of the current embodiment is used as acapacitor electrode, the leak current of an MIM structure can be largelyreduced. FIG. 8 is a schematic view illustrating the energy levels of ametal film formed by performing the TiN film-forming process S5 and theNi film-forming process S8 once. In this case, as described above, thework function of the metal film having a structure in which a TiN filmand a Ni film are stacked can approach almost the same level (forexample, 5.0 eV) as the work function of the Ni film (about 5.15 eV).Therefore, if a TiO₂ film is used as an insulating film, a conductionband offset of about 1.4 eV can be ensured, and thus leak current can belargely reduced. In addition, FIG. 9 is a schematic view illustratingthe energy levels of a metal film formed by setting the TiN film-formingprocess S5 and the Ni film-forming process S8 as one cycle andperforming the cycle a plurality of times. In this case, as describedabove, the work function of the metal film having a structure in whichTiN films and Ni films are stacked can be adjusted to a desired value(for example, 4.8 eV) in the range of, for example, 4.6 eV to 5.0 eV.Therefore, if a TiO₂ film is used as an insulating film, a conductionband offset can be set to a desired value (for example, 1.2 eV) in therange of 1.0 eV to 1.4 eV, and thus leak current can be effectivelyreduced.

(d) In addition, according to the current embodiment, a second metalfilm having a work function greater than 4.8 eV is formed by using a Nifilm which is a metal film (non-noble metal film), instead of using anexpensive noble metal film such as an Au, Ag, Pt, Pd, Rh, Ir, Ru, or Osfilm. In this way, manufacturing costs of semiconductor devices can bereduced.

(e) In addition, according to the current embodiment, in a metal filmhaving a stacked structure of a TiN film and a Ni film, the Ni film isformed by a CVD method. Therefore, the total film-forming rate of themetal film can be increased as compared with the case of using only anALD method, and the throughput can be improved.

<Other Embodiments of the Present Invention>

In the above-described embodiment, a liquid source filled in the bubbleris vaporized by bubbling. However, the present invention is not limitedthereto. For example, the liquid source may be vaporized by using avaporizer instead of using the bubbler.

Furthermore, in the above-described embodiment, TiCl₄ is used as a Tisource in the TiN film-forming process S5. However, the presentinvention is not limited thereto. For example, a Ti source such as TDMAT(tetrakis(dimethylamino)titanium: Ti[N(CH₃)₂]₄) may be used instead ofTiCl₄.

Furthermore, in the above-described embodiment, a TiO₂ film having ahigh permittivity is used as an insulating film. However, the presentinvention is not limited thereto. For example, the present invention canbe applied to the case of using another insulating film or a highpermittivity insulating film such as a hafnium oxide (HfO₂) film, azirconium oxide (ZrO₂) film, a niobium oxide (Nb₂O₅) film, a tantalumoxide (Ta₂O₅) film, a hafnium oxide film doped with aluminum (HfAlOfilm), a zirconium oxide film doped with aluminum (ZrAlO film), astrontium titanate (SrTiO) film, a barium strontium titanate (BaSrTiO)film, and a lead zirconate titanate (PZT) film.

Furthermore, in the above-described embodiment, a TiN film is used as afirst metal film. However, the present invention is not limited thereto.For example, the present invention can be properly applied to the casewhere another film, such as a tantalum nitride (TaN) film, a titaniumaluminum nitride (TiAlN) film, or tantalum aluminum nitride (TaAlN)film, is used as a first metal film. All the TaN film, the TiAlN film,and the TaAlN film have an oxidation resistance greater than that of asecond metal film (Ni film). Furthermore, all the TaN film, the TiAlNfilm, and the TaAlN film have an oxidation resistance greater than thatof a TiN film and can be usefully used as an oxidation barrier film. TheTaN film is a conductive metal nitride film, the TiAlN film is aconductive composite metal film and the TaAlN film is a conductivecomposite metal film.

Furthermore, in the above-described embodiment, a Ni film is used as asecond metal film. However, the present invention is not limitedthereto. For example, the present invention can be properly applied tothe case where a non-noble metal film having a work function greaterthan 4.8 eV, such as a beryllium (Be) film, a carbon (C) film, a cobalt(Co), a selenium (Sc) film, a tellurium (Te) film, or a rhenium (Re)film, is used as a second metal All the listed films are conductiveelemental metal films. FIG. 10 is a table illustrating a group of metalshaving work fractions higher than 4.8 eV which can be used for forming asecond metal film.

EXAMPLES

Hereinafter, examples 1 and 2 of the present invention will be describedtogether with a conventional example and a comparative example withreference to FIG. 12 to FIG. 16.

Example 1

FIG. 12 is a schematic view for explaining a stacked structure of theexample 1 (sample B) of the present invention together with a stackedstructure of the conventional example (sample A) and a stacked structureof the comparative example (sample C).

In addition, FIG. 11 is a flowchart for explaining processes of formingthe sample A (conventional example), the sample B (example 1), and thesample C (comparative example) that are illustrated in FIG. 12.

As shown in FIG. 11, to make the sample B (example 1), first, a surfacetreatment (cleaning) was performed to a silicon substrate (Si-sub) byusing hydrogen fluoride (HF) (HF treatment). Next, a TiN film was formedon the silicon substrate as a bottom electrode (bottom metaldeposition). Next, a HfO₂ film doped with Al (HfAlO film) was formed onthe TiN film as a capacitor insulating film (High-k film) (high-kdeposition). Here, the ratio of Hf and Al included in the capacitorinsulating film was set to be 19:1. Then, a post deposition annealing(PDA) was performed at 700° C., and then a process similar to thepredetermined-time executing process S9 of the above-describedembodiment was performed by using the substrate processing apparatus ofthe above-described embodiment so as to form a stacked structure(Ni/TiN-laminate structure) in which a plurality of TiN films and aplurality of Ni films were alternately stacked (top metal deposition).In the case of the sample B, the TiN film was first formed when formingthe stacked structure (TiN start), and the stacked structure was formedin a manner such that the TiN film was formed between the Ni film andthe HfAlO film. Here, the thicknesses of the TiN film and the Ni filmwere set to 1 nm, respectively, and the execution number of thepredetermined-time executing process S9 was set to five so that thethickness of the stacked structure can be 10 nm. Then, a process similarto the TiN cap film-forming process S12 of the above-describedembodiment was performed to form a TiN film (TiN cap film) having athickness of 50 nm on the stacked structure of the TiN films and the Nifilms (TiN deposition). In this way, a metal film (a stacked filmconstituted by the stacked structure of the TiN films and the Ni films,and the TiN cap film formed on the stacked structure) was formed as atop electrode. Then, a gate structure was patterned by photolithography(gate patterning), and after a forming gas annealing (FGA) treatment wasperformed at 400° C., an Al film was formed on the backside of thesilicon substrate (backside Al deposition).

The sample C (comparative example) was prepared by forming a stackedstructure (Ni/TiN-laminate structure) in which Ni films and TiN filmswere alternately stacked on a capacitor insulating film (top metaldeposition). In the case of the sample C, the Ni film was first formedwhen forming the stacked structure (Ni start), and the stacked structurewas formed in a manner such that the Ni film made direct contact with aHfAlO film. Other film-forming flows and conditions were set to be equalto those of the sample B.

The sample A (conventional example) was prepared by forming a one-layerTiN film on a capacitor insulating film as a top electrode (TiN),instead of forming a stacked structure (Ni/TiN-laminate structure) inwhich Ni films and TiN films were alternately stacked on the capacitorinsulating film. Furthermore, in the sample A, a TiN cap film having athickness of 50 nm was not formed. Other film-forming flows andconditions were set to be equal to those of the sample B.

FIG. 13 is a graph illustrating the equivalent oxide thicknesses (EOTs)of the sample A (conventional example), the sample B (example 1), andthe sample C (comparative example) illustrated in FIG. 12. In FIG. 13,the vertical axis denotes EOT (nm), and the horizontal axis denotes thesamples. Referring to FIG. 13, the EOT of the sample B (example 1) is0.80 nm or less, which is almost not increased as compared with the EOTof the sample A (conventional example) in which a single layer of TiNhaving a high oxidation resistance is formed. However, the EOT of thesample C (comparative example), in which the stacked structure is formedin a manner such that a Ni film makes direct contact with the HfAlOfilm, is increased to 1.40 nm. This may be because the Ni film isoxidized by an oxygen component included in the HfAlO film. That is,like in the case of the sample B, if formation of a stacked structure isstarted from formation of a TiN film (TiN start) to dispose the TiN filmbetween a Ni film and a HfAlO film, oxidation of the Ni film can beeffectively suppressed.

FIG. 14 is a graph illustrating relationships between leak currentdensities (Jg) and EOTs of the sample A (conventional example), thesample B (example 1), and the sample C (comparative example) illustratedin FIG. 12. In FIG. 14, the vertical axis denotes leak current density(Jg, A/cm²) when a voltage of −1 V is applied between top and bottomelectrodes, and the horizontal axis denotes EOT (nm). Furthermore, inFIG. 14, the symbol ♦ denotes the sample A (conventional example), thesymbol ▴ denotes the sample B (example 1), and the symbol ⋄ denotes thesample C (comparative example). Referring to FIG. 14, as compared withthe sample A (symbol ♦), the EOT of the sample B (symbol ▴) is almostnot increased and the leak current density (Jg) of the sample B isdecreased by one digit, in addition, as compared with the sample A(symbol ♦), the leak current density (Jg) of the sample C (symbol ⋄) isdecreased by one digit, but the EOT of the sample C (symbol ⋄) islargely increased. That is, like in the case of the sample B, if a TiNfilm is disposed between a Ni film and a HfAlO film, an increase of EOTcan be suppressed, and along with this, leak current can be decreased.

FIG. 15 is a graph illustrating relationships between leak currentdensities (Jg) and applied voltages of the sample A (conventionalexample), the sample B (example 1), and the sample C (comparativeexample) illustrated in FIG. 12. In FIG. 15, the vertical axis denotesleak current density (Jg, A/cm²), and the horizontal axis denotesvoltage applied between top and bottom electrodes. Furthermore, in FIG.15, the dashed-dotted line denotes the sample A (conventional example),the solid line denotes the sample B (example 1), and the dashed linedenotes the sample C (comparative example). Referring to FIG. 15, in ageneral range (±1 V) of voltage applied between capacitor electrodes,the leak current densities (Jg) of the sample B (solid line) and thesample C (dashed line) are smaller than the leak current density (Jg) ofthe sample A (convention example). That is, like in the case of thesample B, if a stacked structure of TiN films and Ni films is formed,leak current can be decreased.

Example 2

FIG. 16A is a schematic view illustrating the stacked structure of anexample 2 (sample D) of the present invention. In the sample D, a metalfilm was formed as a gate electrode by stacking a one-layer TiN film anda one-layer Ni film on a SiO₂ film functioning as a gate insulatingfilm. The TiN film was formed to be disposed between the Ni film and theSiO₂ film. In addition, while varying the thickness of the TiN film to0.2 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, and 10 nm, a plurality of sampleshaving different thickness TiN films were prepared. The thickness of theNi film was set to 20 nm.

FIG. 16B is a graph illustrating a relationship between the workfunction of the metal film and the thickness of the TiN film of thesample D together with those of the sample B and sample C. In FIG. 16B,the vertical axis denotes the work function (eV) of metal films, and thehorizontal axis denotes the thickness (nm) of the TiN film of the sampleD (example 2). In FIG. 16B, the symbol □ denotes the work function ofthe metal film of the sample D, the solid line denotes the work functionof the metal film of the sample C, and the dashed line denotes the workfunction of the metal film of the sample B. Referring to FIG. 16B, inthe range where the thickness of the TiN film of the sample D is 4 nm orless, the effective work function of the entire metal film having astacked structure of the TiN film and the Ni film can approach the workfunction of the Ni film (about 5.15 eV). However, when the thickness ofthe TiN film is greater than 4 nm, since the effect of the work functionof TiN increases, the effective work function of the entire metal filmis decreased. Therefore, it is preferable that the thickness of the TiNfilm is 4.0 nm or less.

<Another Embodiment of the Invention>

Furthermore, in the above-described embodiments, an explanation has beengiven on the case of performing a film-forming process using asingle-wafer type substrate processing apparatus configured to process asubstrate at a time. However, the present invention is not limitedthereto. For example, a batch type vertical apparatus configured toprocess a plurality of substrates at a time may be used as a substrateprocessing apparatus to perform a substrate processing process.

FIG. 17A and FIG. 17B are schematic views illustrating a verticalprocess furnace 302 of a vertical apparatus that can be suitably usedaccording to an embodiment of the present invention, in which FIG. 17Ais a vertical sectional view of the process furnace 302, and FIG. 17B isa sectional view of the process furnace 302 taken along line A-A of FIG.17A.

As shown in FIG. 17A, the process furnace 302 includes a heater 307 as aheating unit (heating mechanism). The heater 307 has a cylindrical shapeand is supported on a holding plate such as a heater base so that theheater 307 can be vertically fixed.

Inside the heater 307, a process tube 303 is installed concentricallywith the heater 307 as a reaction tube. The process tube 303 is made ofa he-at-resistant material such as quartz (SiO₂) and silicon carbide(SiC) and has a cylindrical shape with a closed top side and an openedbottom side. In the hollow part of the process tube 303, a processchamber 301 is formed, which is configured to accommodate substratessuch as wafers 200 in a state where the wafers 200 are horizontallypositioned and vertically arranged in multiple stages in a boat 317(described later).

At the lower side of the process tube 303, a manifold 309 is installedconcentrically with the process tube 303. The manifold 309 is made of amaterial such as stainless steel and has a cylindrical shape with openedtop and bottom sides. The manifold 309 is engaged with the process tube303 and installed to support the process tube 303. Between the manifold309 and the process tube 303, an O-ring 320 a is installed as a sealmember. The manifold 309 is supported by the heater base such that theprocess tube 303 can be vertically fixed. The process tube 303 and themanifold 309 constitute a reaction vessel.

A first nozzle 333 a as a first gas introducing part, and a secondnozzle 333 b as a second gas introducing part are connected to themanifold 309 in a manner such that the first and second nozzles 333 aand 333 b penetrate the sidewall of the manifold 309. Each of the firstand second nozzles 333 a and 333 b has an L-shape with a horizontal partand a vertical part. The horizontal part is connected to the manifold309, and the vertical part is erected in an arc-shaped space between theinner wall of the process tube 303 and the wafers 200 along the innerwall of the process tube 303 from the lower side to the upper side inthe arranged direction of the wafers 200. In the lateral sides of thevertical parts of the first and second nozzles 333 a and 333 b, firstgas supply holes 348 a and second gas supply holes 348 b are formed,respectively. The first and second gas supply holes 348 a and 348 b havethe same size and are arranged at the same pitch from the lower side tothe upper side.

The same gas supply systems as those explained in the previousembodiment are connected to the first and second nozzles 333 a and 333b. However, the current embodiment is different from the previousembodiment, in that the first source gas supply system and the secondsource gas supply system are connected to the first nozzle 333 a, andthe reaction gas supply system is connected to the second nozzle 333 b.That is, in the current embodiment, source gases (the first source gasand the second source gas) are supplied through a nozzle different froma nozzle used to supply a reaction gas. Alternatively, the first sourcegas and the source gas may be supplied through different nozzles.

At the manifold 309, an exhaust pipe 331 is installed to exhaust theinside atmosphere of the process chamber 301. A vacuum exhaust devicesuch as a vacuum pump 346 is connected to the exhaust pipe 331 through apressure detector such a pressure sensor 345 and a pressure regulatorsuch as an auto pressure controller (APC) valve 342, and based onpressure information detected by the pressure sensor 345, the APC valve342 is controlled so that the inside of the process chamber 301 can bevacuum-evacuated to a predetermined pressure (vacuum degree). The APCvalve 342 is an on-off valve configured to be opened and closed to startand stop vacuum evacuation of the inside of the process chamber 301, andconfigured to be adjusted in valve opening degree for adjusting theinside pressure of the process chamber 301.

At the lower side of the manifold 309, a seal cap 319 is installed as afurnace port cover capable of hermetically closing the opened bottomside of the manifold 309. The seal cap 319 is configured to be broughtinto contact with the manifold 309 in a vertical direction from thebottom side of the manifold 309. The seal cap 319 is made of a metalsuch as stainless steel and has a circular disk shape. On the topsurface of the seal cap 319, an O-ring 320 b is installed as a sealmember configured to make contact with the bottom side of the manifold309. At a side of the seal cap 319 opposite to the process chamber 301,a rotary mechanism 367 is installed to rotate the boat 317 (describedlater). A rotation shaft 355 of the rotary mechanism 367 is insertedthrough the seal cap 319 and is connected to the boat 317, so as torotate the wafers 200 by rotating the boat 317. The seal cap 319 isconfigured to be vertically moved by a boat elevator 315 which isdisposed at the outside of the process tube 303 as an elevatingmechanism, and by this, the boat 317 can be loaded into and out of theprocess chamber 301.

The boat 317 which is a substrate holding tool is made of aheat-resistant material such as quartz or silicon carbide and isconfigured to hold a plurality of wafers 200 in a state where the wafers200 are horizontally positioned and arranged in multiple stages with thecenters of the wafers 200 being aligned. At the lower part of the boat317, an insulating member 318 made of a heat-resistant material such asquartz or silicon carbide is installed to prevent heat transfer from theheater 307 to the seal cap 319. In the process tube 303, a temperaturesensor 363 is installed as a temperature detector, and based ontemperature information detected by the temperature sensor 363, powersupplied to the heater 307 is controlled to obtain a desired temperaturedistribution in the process chamber 301. Like the first nozzle 333 a andthe second nozzle 333 b, the temperature sensor 363 is installed alongthe inner wall of the process tube 303.

A controller 380 which is a controller (control part) is configured tocontrol operations of parts such as the APC valve 342, the heater 307,the temperature sensor 363, the vacuum pump 346, the rotary mechanism367, the boat elevator 315, the valves va1 to va5, vb1 to vb5, ve1, tovc3, vd1 and vd2, and ve1 to ve3, and the MFCs 222 a, 222 b, 222 c, 222d, and 222 e.

Next, an explanation will be given on a substrate processing processwhich is one of semiconductor device manufacturing processes for forminga thin film on a wafer 200 by a CVD method using the process furnace 302of the vertical apparatus. In the following description, each part ofthe vertical apparatus is controlled by the controller 380.

A plurality of wafers 200 are charged into the boat 317 (wafercharging). Then, as shown in FIG. 17A, the boat 317 in which theplurality of wafers 200 are held is lifted and loaded into the processchamber 301 by the boat elevator 315 (boat loading). In this state, thebottom side of the manifold 309 is sealed by the seal cap 319 with theO-ring 320 b being disposed therebetween.

The inside of the process chamber 301 is vacuum-evacuated to a desiredpressure (vacuum degree) by the vacuum pump 346. At this time, theinside pressure of the process chamber 301 is measured by the pressuresensor 345, and based on the measured pressure, the APC valve 342 isfeedback-controlled. In addition, the inside of the process chamber 301is heated to a desired temperature by the heater 307. At this time, soas to obtain a desired temperature distribution in the process chamber301, power to the heater 307 is feedback-controlled based on temperatureinformation detected by the temperature sensor 363. Then, the rotarymechanism 367 rotates the boat 317 to rotate the wafers 200.

Then, according to a sequence similar to the sequence of the TiNfilm-forming process S5 to the TiN cap film-forming process S12, metalfilms having a stacked structure constituted by a TiN film and a Ni filmare formed on TiO₂ films previously formed on the wafers 200, and thenTiN films (TiN cap films) having a predetermined thickness are formed onthe metal films. Thereafter, according to a sequence similar to theremaining gas removing process S13, a remaining gas removing process isperformed.

After that, the boat elevator 315 lowers the seal cap 319 to open thebottom side of the manifold 309 and unload the boat 317 from the processtube 303 through the opened bottom side of the manifold 309 in a statewhere the wafers 200 on which the metal films and the TiN cap filmshaving predetermined thicknesses are formed are held in the boat 317(boat unloading). Thereafter, the processed wafers 200 are dischargedfrom the boat 317 (wafer discharging).

Although the vertical apparatus is used in the current embodiment,processes similar to the substrate processing processes of theabove-described embodiment can be performed to obtain similar effects.

<Another Embodiment of the Invention>

In the above-described embodiments, an explanation has been given on thecase where a TiN film and a Ni film are formed in the same processchamber. However, the present invention is not limited thereto. Forexample, a TiN film and a Ni film may be formed in different processchambers. In that case, as shown in FIG. 18, a substrate processingapparatus (cluster apparatus), such as a multi-chamber type substrateprocessing system including a plurality of process chambers, may be usedHereinafter, an explanation will be given on an exemplary case where aTiN film and a Ni film are formed in different process chambers of thecluster apparatus. In the cluster apparatus of the current embodiment,Front Opening Unified Pods (FOUPs, hereinafter referred to as pods) 1are used as wafer carrying carriers (substrate containers) configured tocarry wafers 200.

As shown in FIG. 18, the cluster apparatus 10 includes a first wafertransfer chamber 11 (hereinafter referred to as a negative pressuretransfer chamber 11) as a transfer module (carrying chamber) configuredto endure a pressure (negative pressure) lower than atmosphericpressure, and when viewed from the top, a case 12 (hereinafter referredto as a negative pressure transfer chamber case 12) of the negativepressure transfer chamber 11 has a heptagonal box shape with closed topand bottom sides. The negative pressure transfer chamber case 12 isconfigured as a carrying vessel (airtight vessel). At the center part ofthe negative pressure transfer chamber 11, a wafer transfer machine 13(hereinafter referred to as a negative pressure transfer machine 13) isinstalled as a carrying robot configured to transfer a wafer 200 under anegative pressure condition.

As loadlock modules (loadlock chambers), a carrying-in preliminarychamber 14 (hereinafter referred to as a carrying-in chamber 14) and acarrying-out preliminary chamber 15 (hereinafter referred as acarrying-out chamber 15) are closely disposed and connected to thebiggest sidewall (front wall) of the seven sidewalk of the negativepressure transfer chamber case 12. When viewed from the top, each of acase of the carrying-in chamber 14 and a case of the carrying-outchamber 15 is formed in an approximately rhombic shape with dosed topand bottom sides and is configured as a loadlock chamber capable ofenduring a negative pressure condition.

A second wafer transfer chamber 16 (hereinafter referred to as apositive pressure transfer chamber 16), which is a front end moduleconfigured to be kept at atmospheric pressure or higher (hereinafterreferred to as a positive pressure), is connected to sides of thecarrying-in chamber 14 and the carrying-out chamber 15 opposite to thenegative pressure transfer chamber 11, and when viewed from the top, acase of the positive pressure transfer chamber 16 has a horizontallyelongated rectangular shape with closed top and bottom sides, Betweenthe carrying-in chamber 14 and the positive pressure transfer chamber16, a gate valve 17A is installed, and between the carrying-in chamber14 and the negative pressure transfer chamber 11, a gate valve 17B isinstalled. Between the carrying-out chamber 15 and the positive pressuretransfer chamber 16, a gate valve 18A is installed, and between thecarrying-out chamber 15 and the negative pressure transfer chamber 11, agate valve 18B is installed. In the positive pressure transfer chamber16, a second wafer transfer machine 19 (hereinafter referred to as apositive pressure transfer machine 19) is installed as a carrying robotconfigured to transfer a wafer 200 under a positive pressure condition.The positive pressure transfer machine 19 is configured to be movedupward and downward by an elevator installed at the positive pressuretransfer chamber 16, and is also configured to reciprocate left andright by a linear actuator. At the left end part of the positivepressure transfer chamber 16, a notch aligning device 20 is installed.

At the front wall of the positive pressure transfer chamber 16, threewafer carrying entrances 21, 22, and 23 are formed in a closed arrangedfashion so that wafers 200 can be carried into and out of the positivepressure transfer chamber 16 through the wafer carrying entrances 21,22, and 23. Pod openers 24 are installed at the wafer carrying entrances21, 22, and 23, respectively. Each of the pod openers 24 includes astage 25 on which a pod 1 can be placed, and a cap attachment/detachmentmechanism 26 configured to attach/detach a cap to/from a pod 1 placed onthe stage 25. By attaching/detaching a cap to/from a pod 1 placed on thestage 25 by using the pod opener 24, a wafer taking in/out entrance ofthe pod 1 can be dosed or opened. Pods 1 are supplied to the stages 25of the pod openers 24 and taken away from the stages 25 of the podopeners 24 by an in-process carrying device (rail guided vehicle, RGV).

As shown in FIG. 18, as processing modules, a first process unit 31 (TiNfilm-forming unit 31) and a second process unit 32 (Ni film-forming unit32) are closely disposed and respectively connected to two sidewalk rearwalls) of the seven sidewalls of the negative pressure transfer chambercase 12 opposite to the positive pressure transfer chamber 16. The firstprocess unit 31 and the second process unit 32 have a structure similarto the substrate processing apparatus of the above-described embodiment.A first source supply system and a reaction gas supply system areinstalled at the first process unit 31 but a second source supply systemis not installed at the first process unit 31, and a second sourcesupply system is installed at the second process unit 32 but a firstsource supply system and a reaction gas supply system are not installedat the second process unit 32. This is a difference from theabove-described embodiment.

Between the first process unit 31 and the negative pressure transferchamber 11, a gate valve 44 is installed. Between the second processunit 32 and the negative pressure transfer chamber 11, a gate valve 118is installed. In addition, as cooling stages, a first cooling unit 35and a second cooling unit 36 are respectively connected to two sidewalkof the seven sidewalk of the negative pressure transfer chamber case 12that face the positive pressure transfer chamber 16, and each of thefirst and second cooling units 35 and 36 functions as a cooling chamberfor cooling a processed wafer 200.

The cluster apparatus 10 includes a main controller 37 for overallcontrolling of substrate processing flows. The main controller 37controls each part of the cluster apparatus 10.

Next, process that a metal film having a stacked structure constitutedby a TiN film and a Ni film is formed on a TiO₂ film previously formedon a wafer 200, and then a TiN film (TiN cap film) having apredetermined thickness is formed on the metal film will now beexplained. In the following description, each part of the clusterapparatus 10 is controlled by the main controller 37.

A cap of a pod 1 placed on the stage 25 of the cluster apparatus 10 isdetached by the cap attachment/detachment mechanism 26, and thus a wafertaking in/out entrance of the pod 1 is opened. After the pod 1 isopened, the positive pressure transfer machine 19 installed at thepositive pressure transfer chamber 16 picks up wafers 200 one by onefrom the pod 1 through the wafer carrying entrance and carries thewafers 200 to the carrying-in chamber 14 where the wafers 200 are placedon a carrying-in chamber temporary stage. During this operation, thegate valve 17A disposed at a side of the carrying-in chamber 14 facingthe positive pressure transfer chamber 16 is in an opened state; thegate valve 17B disposed at the other side of the carrying-in chamber 14facing the negative pressure transfer chamber 11 is in a closed state;and the inside of the negative pressure transfer chamber 11 is kept at,for example, 100 Pa.

The side of the carrying-in chamber 14 facing the positive pressuretransfer chamber 16 is closed by the gate valve 17A, and the carrying-inchamber 14 is exhausted to a negative pressure by an exhaust device.When the inside pressure of the carrying-in chamber 14 is reduced to apreset pressure, the gate valve 17B disposed at the other side of thecarrying-in chamber 14 facing the negative pressure transfer chamber 11is opened. Next, the negative pressure transfer machine 13 of thenegative pressure transfer chamber 11 picks up the wafers 200 one by onefrom the carrying-in chamber temporary stage and carries the wafers 200into the negative pressure transfer chamber 11. Thereafter, the gatevalve 179 disposed at the other side of the carrying-in chamber 14facing the negative pressure transfer chamber 11 is closed.

Subsequently, the gate valve 44 of the first process unit 31 is opened,and the negative pressure transfer machine 13 loads the wafer 200 into aprocess chamber of the first process unit 31 (wafer loading). When thewafer 200 is loaded into the process chamber of the first process unit31, since the carrying-in chamber 14 and the negative pressure transferchamber 11 are previously vacuum-evacuated, permeation of oxygen ormoisture into the process chamber of the first process unit 31 can besurely prevented. Then, according to a sequence similar to the sequenceof the pressure adjusting process S3 to the TiN film-forming process S5of the above-described embodiment, a TiN film is formed on a TiO₂ filmpreviously formed on the wafer 200. After that, in the reverse sequenceto the above-described sequence, the wafer 200 on which the TiN film isformed to have a predetermined thickness is unloaded from the processchamber of the first process unit 31 to the negative pressure transferchamber 11.

Subsequently, the gate valve 118 of the second process unit 32 isopened, and the negative pressure transfer machine 13 loads the wafer200 into a process chamber of the second process unit 32 (waferloading). When the wafer 200 is loaded into the process chamber of thesecond process unit 32, since the carrying-in chamber 14 and thenegative pressure chamber 11 are previously vacuum-evacuated, permeationof oxygen or moisture into the process chamber of the second processunit 32 can be surely prevented. Then, according to a sequence similarto the sequence of the pressure adjusting process S6 to the Nifilm-forming process S8 of the above-described embodiment, a Ni film isformed on the TiN film formed over the wafer 200 in the first processunit 31. After that, in the reverse sequence to the above-describedsequence, the wafer 200 over which the Ni film is formed to have apredetermined thickness is unloaded from the process chamber of thesecond process unit 32 the negative pressure transfer chamber 11.

Then, according to a sequence similar to the sequence of thepredetermined-time executing process S9 of the above-describedembodiment, the TiN film-forming process using the first process unit 31and the Ni film-forming process using the second process unit 32 are setas one cycle, and the cycle is performed predetermined times so as toform a metal film having a stacked structure of TiN film and Ni film onthe TiO₂ film previously formed on the wafer 200.

Subsequently, the gate valve 44 of the first process unit 31 is opened,and the negative pressure transfer machine 13 loads the wafer 200 intothe process chamber of the first process unit 31 (wafer loading). Then,according to a sequence similar to the sequence of the pressureadjusting process S10 to the TiN cap film-forming process S12, a TiNfilm (TiN cap film) having a predetermined thickness is formed on themetal film having a stacked structure of TiN film and Ni film. Afterthat, in the reverse sequence to the above-described sequence, the wafer200 over which the TiN film is formed to have a predetermined thicknessis unloaded from the process chamber of the first process unit 31 to thenegative pressure transfer chamber 11.

Thereafter, the side of the carrying-out chamber 15 facing the negativepressure chamber 11 is opened by the gate valve 18B, and the negativepressure transfer machine 13 carries the wafer 200 from the negativepressure chamber 11 to the carrying-out chamber 15, and the wafer 200 istransferred to a carrying-out chamber temporary stage. For this, theside of the carrying-out chamber 15 facing the positive pressuretransfer chamber 16 is previously closed by the gate valve 18A, and thecarrying-out chamber 15 is exhausted to a negative pressure by anexhaust device. After the pressure of the car chamber 15 is decreased toa preset value, the side of the carrying-out chamber 15 facing thenegative pressure chamber 11 is opened by the gate valve 18B, and thewafer 200 is unloaded. After the wafer 200 is unloaded, the gate valve18B is closed.

By repeating the above-described actions, twenty five wafers 200batch-loaded in the chamber 14 can be sequentially processed through theabove-described processes. After the twenty five wafers 200 aresequentially processed, the processed wafers 200 are collected on thetemporary stage of the carrying-out chamber 15.

Thereafter, nitrogen gas is supplied into the carrying-out chamber 15which is kept at a negative pressure so as to adjust the inside pressureof the carrying-out chamber 15 to atmospheric pressure, and then theside of the car chamber 15 facing the positive pressure transfer chamber16 is opened by the gate valve 18A. Next, a cap of an empty pod 1 placedon the stage 25 is opened by the cap attachment/detachment mechanism 26of the pod opener 24. Subsequently, the positive pressure transfermachine 19 of the positive pressure transfer chamber 16 picks up thewafers 200 from the carrying-out chamber 15 to the positive pressuretransfer chamber 16 and carries the wafers 200 into the pod 1 throughthe wafer carrying entrance 23 of the positive pressure transfer chamber16. After the processed twenty five wafers 200 are carried into the pod1, the cap of the pod 1 is attached to the wafer taking in/out entranceof the pod 1 by the cap attachment/detachment mechanism 26 of the podopener 24 so that the pod 1 is closed.

A process similar to the substrate processing process of theabove-described embodiment can be performed by using the clusterapparatus 10 of the current embodiment, and effects similar to those ofthe above-described embodiment can be obtained. In the case whereprocess conditions (particularly, a process temperature) for forming afirst metal film are different from process conditions (particularly, aprocess temperature) for forming a second metal film, the first andsecond metal films may be formed in different process chambers like inthe current embodiment.

Furthermore, examples of a gate electrode forming process include: agate first process in which a source/drain diffusion layer is formed byperforming about 1000-° C. annealing, that is, activation annealing(spike annealing) after a gate electrode is formed; and a gate lastprocess in which such a source/drain diffusion layer is formed before agate electrode is formed. In the case of a gate first process, a gateelectrode is heated to about 1,000° C. during activation annealing, andthus the present invention may be unsuitable for a gate first processbecause a TiN film does not have oxidation resistance in a temperatureregion of about 1,000° C. However, in the case of a gate last process, agate electrode is not heated to a temperature about 1,000° C., and a TiNfilm has oxidation resistance in temperature regions of processes thatare performed after the gate electrode is formed. Thus, the presentinvention may be suitable for a gate last process. That is, the presentinvention can be suitably applied to the case where a gate electrode isformed through a gate last process. Furthermore, in a process ofmanufacturing a dynamic random access memory (DRAM), annealing isperformed at about 400° C. under a H₂-gas atmosphere after a capacitorelectrode is formed. In a DRAM manufacturing process, a capacitorelectrode is heated to about 400° C. at most, and in such a temperaturecondition, TiN has high oxidation resistance as compared with Ni. Thatis, the present invention can be suitably applied to the case where acapacitor electrode of a DRAM is manufactured.

As described above, the present invention provides a semiconductordevice including a metal film which can be formed with lower costs buthave a necessary work function and oxidation resistance. In addition,according to the present invention, there are provided a method ofmanufacturing a semiconductor device and a substrate processingapparatus, which are designed to form a metal film having a necessarywork function and oxidation resistance with lower costs.

<Supplementary Note>

The present invention also includes the following preferred embodiments.

According to an embodiment of the present invention, there is provided asemiconductor device including: an insulating film disposed on asubstrate; and a metal film disposed adjacent to the insulating film,wherein the metal film includes a stacked structure of a first metalfilm and a second metal film, an oxidation resistance of the first metalfilm is greater than that of the second metal film, the second metalfilm has a work function greater than 4.8 eV and is different from thefirst metal film in material, and the first metal film is disposedbetween the second metal film and the insulating film.

Preferably, the metal film is disposed on the insulating film, andfurther includes the first metal lilt disposed on an outermost surfacethereof.

Preferably, the stacked structure is repeatedly stacked in the metalfilm.

Preferably, a thickness of the first metal film ranges from 0.2 nm to 4nm.

Preferably, a thickness of the second metal ranges from 0.5 nm to 10 nm.

Preferably, a thickness of the second metal film ranges from 4 nm to 5nm.

Preferably, the second metal film is thicker than the first racial film.

Preferably, the first metal film includes one of a titanium nitridefilm, a tantalum nitride film, a titanium aluminum nitride film, and atantalum aluminum nitride film.

Preferably, the second metal film includes a non-noble metal.

Preferably, the second metal film includes at least one of a nickelfilm, a cobalt film, a beryllium film, a carbon film, a selenium film, atellurium film and a rhenium film.

Preferably, the insulating film includes a high permittivity film.

Preferably, the insulating film includes at least one of a hafnium oxidefilm. zirconium oxide film, a hafnium oxide film doped with an aluminum,a zirconium oxide film doped with the aluminum, a titanium oxide film, aniobium oxide film, a tantalum oxide film, a strontium titanate film, abarium strontium titanate film and a lead zirconate titanate film.

According to another embodiment of the present invention, there isprovided a method of manufacturing a semiconductor device, the methodincluding: forming an insulating film on a substrate; and forming ametal film including a stacked structure of a first metal film and asecond metal film adjacent to the insulating film, the first metal filmbeing formed between the second metal film and the insulating film,wherein an oxidation resistance of the first metal filet is greater thanthat of the second metal film, and the second metal film has a workfunction greater than 4.8 eV and is different from the first metal filmin material.

According to another embodiment of the present invention, there isprovided a substrate processing apparatus including: a process chamberconfigured to process a substrate; a first process gas supply systemconfigured to supply a first process gas into the process chamber toform a first metal film; a second process gas supply system configuredto supply a second process gas into the process chamber to form a secondmetal film; and a controller configured to control the first process gassupply system and the second process gas supply system, wherein anoxidation resistance of the first metal film is greater than that of thesecond metal film, the second metal film has a work function greaterthan 4.8 eV and is different from the first metal film in material, andthe controller controls the first process gas supply system and thesecond process gas supply system to form a metal film having a stackedstructure of the first metal film and the second metal film adjacent toan insulating film disposed on the substrate by supplying the firstprocess gas and the second process gas into the process chamber wherethe substrate is accommodated such that the first metal film is formedbetween the second metal film and the insulating film.

According to another embodiment of the present invention, there isprovided a substrate processing apparatus including: a first processchamber configured to process a substrate; a first process gas supplysystem configured to supply a first process gas into the first processchamber to form a first metal film; a second process chamber configuredto process the substrate; a second process gas supply system configuredto supply a second process gas into the second process chamber to form asecond metal film; a carrying chamber disposed between the first processchamber and the second process chamber for carrying the substrate; acarrying robot installed in the carrying chamber to carry the substratebetween the first process chamber and the second process chamber; and acontroller configured to control the first process gas supply system,the second process gas supply system and the carrying robot, wherein anoxidation resistance of the first metal film is greater than that of thesecond metal film, the second metal film has a work function greaterthan 4.8 eV and is different from the first metal film in material, andthe controller controls the first process gas supply system, the secondprocess gas supply system and the carrying robot to form a metal filmhaving a stacked structure of the first metal film and the second metalfilm adjacent to an insulating film disposed on the substrate bycarrying the substrate into the first process chamber, supplying thefirst process gas into the first process chamber, carrying the substrateinto the second process chamber, and supplying the second process gasinto the process chamber such that the first metal film is formedbetween the second metal film and the insulating film.

What is claimed is:
 1. A semiconductor device comprising: an insulatingfilm disposed on a substrate; and a metal film comprising a stackedstructure of: a laminated film where a first metal film and a secondmetal film are laminated repeatedly; and a capping metal film disposedon the laminated film, the first metal film at a bottom of the metalfilm being disposed on the insulating film to directly contact theinsulating film, the capping metal film being disposed on the secondmetal film at a top of the metal film to directly contact the secondmetal film, the second metal film having a work function greater than4.8 eV and being different from the first metal film in material, andthe capping metal film being constituted by a same material as the firstmetal film, wherein oxidation resistances of the first metal film andthe capping metal film are greater than that of the second metal film.2. The semiconductor device of claim 1, wherein a thickness of the firstmetal film ranges from 0.2 nm to 4 nm.
 3. The semiconductor device ofclaim 1, wherein a thickness of the second metal film ranges from 0.5 nmto 10 nm.
 4. The semiconductor device of claim 1, wherein a thickness ofthe second metal film ranges from 4 nm to 5 nm.
 5. The semiconductordevice of claim 1, wherein the second metal film is thicker than thefirst metal film.
 6. The semiconductor device of claim 1, wherein thefirst metal film comprises one of a titanium nitride film, a tantalumnitride film, a titanium aluminum nitride film and a tantalum aluminumnitride film.
 7. The semiconductor device of claim 1, wherein the secondmetal m comprises a non-noble metal.
 8. The semiconductor device ofclaim 1, wherein the second metal film comprises at least one of anickel film, a cobalt film, a beryllium film, a carbon film, a seleniumfilm, a tellurium film and a rhenium film.
 9. The semiconductor deviceof claim 1, wherein the insulating film comprises a high permittivityfilm.
 10. The semiconductor device of claim 1, wherein the insulatingfilm comprises at least one of a hafnium oxide film, a zirconium oxidefilm, a hafnium oxide film doped with an aluminum, a zirconium oxidefilm doped with the aluminum, a titanium oxide film, a niobium oxidefilm, a tantalum oxide film, a strontium titanate film, a bariumstrontium titanate film and a lead zirconate titanate film.
 11. Asemiconductor device comprising: an insulating film disposed on asubstrate; and a metal film comprising a stacked structure of alaminated film where a first metal film and a second metal film arelaminated repeatedly; and a third metal film disposed on the laminatedfilm, the first metal film at a bottom of the metal film being disposedon the insulating film to directly contact the insulating film, thethird metal film being disposed on the second metal film at a top of themetal film to directly contact the second metal film, the second metalfilm having a work function greater than 4.8 eV and being different fromthe first metal film in material, and the third metal being constitutedby a same material as the first metal film, wherein oxidationresistances of the first metal film and the third metal film are greaterthan that of the second metal film.